Human computer interaction has been revolutionized by the graphical user interface (GUI). Namely, this interface provides an efficient means for presenting information to a user with a bandwidth which immensely exceeds any prior channel. Over the years the speed at which information can be presented has increased further through color screens, enlarged displays, intelligent graphical objects (e.g. pop-up windows), window tabs, menus, toolbars and sounds. During this time, however, the input devices have remained essentially unchanged, i.e. the keyboard and the pointing device (e.g. mouse, track ball or touch pad). In recent years, various handwriting devices have also been introduced (e.g. in the form of a stylus or a graphical pen). Nevertheless, while the output bandwidth has multiplied several times, the input ditto has been substantially unaltered. Consequently, a severe asymmetry in the communication bandwidth in the human computer interaction has occurred. In order to compensate for this, and render the data input more efficient and user friendly, various solutions have been proposed.
U.S. Pat. No. 5,367,315 describes a method and an apparatus for controlling cursor movements on a computer screen based on a user's eye and head movements. The system is activated by operating a designated key or switch. Thereafter, the user can position the cursor at any point on the screen by moving the eyes and head in the same manner as the conventional mouse. Specifically, infrared detectors determine the relative position of the user's head within a defined active area, so that the cursor's position on the screen depends on the head's position within the active area. The user's eyes are here primarily used as light reflectors to determine changes in the eye position, and thus indirectly to reveal variations in the head positioning within the active area. Thus, a relationship between the eyes/head position and the cursor position is established.
U.S. Pat. No. 6,215,471 discloses a vision pointer method and apparatus, wherein a user controls the movements of a pointer on a screen by means of a corresponding rotation or movement of a visually identifiable characteristic, such as a facial feature. Moreover, by modifying a changeable visual characteristic, e.g. closing an eye, the user may generate control signals representing mouse clicks and similar functions. Analogous to the solution above, there is also here a close relationship between the positioning of the visually identifiable characteristic and the pointer position on the screen.
U.S. Pat. No. 6,204,828 reveals a computer-driven system for assisting an operator in positioning a cursor on a screen. Here, the system calculates the operator's gaze position on the screen, and initially places the cursor within a gaze area identified by this position. A mechanical input device, e.g. a mouse or a keyboard, is then used to control the cursor from the initial position to an intended end position on the screen.
The first two solutions above are problematic because by employing these strategies it may be difficult for the user, who perhaps is a handicapped person, to control his/her head or gaze with sufficiently high precision to position the cursor at the desired place on the screen. Furthermore, even if the user is capable of controlling his/her body with very high precision, various imperfections in the tracking equipment may introduce measurement errors when registering the eyes/head position and the gaze point respectively, so that it still becomes difficult, or at least wearying to achieve the intended result. The last solution is an improvement in this respect, since here the user can compensate for any errors in gaze position estimations when manipulating the mechanical input device. Nevertheless, operation of such a mechanical device is associated with other problems, for instance related to fatigue, repetitive strain injuries etc. Moreover, a mechanical input device, such as a conventional mouse, is relatively slow and requires a certain operating space, either on the desktop or on a device surface (in the case of a laptop). Sometimes, no such space is available, or providing the required space is problematic.